Bacteriophage-resistant mutants of Salmonella typhimurium deficient in two major outer membrane proteins.

Mutants resistant to bacteriophages (P221 and PH105 or PH51) were isolated from a rfa strain of Salmonella typhimurium. They were found deficient in separate 33,000- to 36,000-dalton band proteins (major band proteins). Double mutants derived from both types of mutants were deficient in both of the bands. The growth behavior of all the mutants was normal. The outer membrane of the mutants appeared to be more wrinkled than normal and formed vesicles in many of the mutants. In freeze-fractured cells, changes were seen in the outer membrane (particleless patches in the concave fracture face, the particles themselves being smaller than normal). These changes were more marked in the double mutants.